This invention relates to the preparation of novel, aqueous solutions of sodium borohydride (NaBH.sub.4) and sodium aluminate (Na.sub.2 Al.sub.2 O.sub.4), and their use in treating metal-bearing wastes. The sodium borohydride removes the dissolved complexed metal ion as a reduced precipitate, while the sodium aluminate serves to coagulate the insoluble particles. (To be useful as commercial products these solutions need sufficient level(s) of alkaline agent(s) to retard the rate of borohydride hydrolysis and thereby minimize the pressure build-up due to the formation of hydrogen.)